Radio navigation devices contain IT-supported technical systems which, with the aid of position determination (satellite, radio, GSM (Global System for Mobile Communications) and inert or autonomous systems) and geo-information (topology, road, air or sea maps) enable destination guidance to a selected location or a route that takes desired criteria into account.
The navigation and positioning of vehicles, transmissions and machines generally takes place on the basis of satellite-supported locating systems. However, the locating data are often not only inherently inaccurate, but totally or partially fail depending on the location, for example in tunnels, gorges or under bridges. At these locations the position determination by means of satellites is either defective and faulty or completely fails, and this is why when these systems fail, other receiving apparatuses or sensors, for example pedometers, compasses, acceleration sensors, have to be used. However, these systems have additive errors, i.e. the longer the failure of the satellite-supported sensor system lasts, the less precise the position calculated from the remaining sensors becomes. In mobile applications location-dependent factors can contribute to the worsening of the quality of individual sensor data. This location-dependent worsening of the data quality may lead to the total failure of entire sensor systems, and in particular it may partially or also totally disrupt the reception of the satellite-supported position determination.
If, for example, a conventional GPS-supported position determination system approaches an interference point, such as for example a tunnel, the GPS connection does not suddenly fail. Rather, the GPS determination becomes less accurate in the transition phase of approaching. This results from the fact that depending on the position, some of the GPS satellites continue to send signals to the interference point, whereas others are already totally blocked by the interference point so that overall, less data suppliers are available from which an error can be averaged. This fact leads disadvantageously to the aforementioned problem that conventional GPS-supported position determination systems increasingly receive faulty data while, for example, driving into a tunnel, onto which they then extrapolate after the failure of the GPS system, and so increase the error further, without taking any appropriate counter-measures.
In addition, the use of some sensor systems is associated with high costs. Position determination by means of WLAN (Wireless Local Area Network) or radio telephone masts requires a considerable amount of energy input and generally also requires a continuous on-line connection.
Essentially two methods are currently known from the prior art in order to improve this situation:
On the one hand, following the failure of the satellite-supported positioning system, triangulation with mobile telephony radio masts with known positions is carried out or comparable radio networks, for example WLAN, are compared with a dynamic data bank. However, this requires an extensive data bank subject to constant change and in which this information is kept and administered. This databank is generally so large that it is not kept locally, but is stored on central servers. Therefore, access to such data banks requires on-line access which is also often disrupted in the problem areas that have been described.
On the other hand, integrated navigation systems carry map data for large regions in which road guides are recorded with which the positions calculated by the remaining sensor system can be corrected with the exclusion of “impossible” positions. However, these map data are expensive because they are marketed commercially and, due to their size, require extensive local memories, for example hard discs or CDs/DVDs. Moreover, they mainly focus on road guides, and not on regional access restrictions such as tunnels, bridges, ferries, gorges. This gives rise, on the one hand, to high costs for maps and their storage, and on the other hand it reduces the problem cases to known roads. However, interference may also occur independently of the course of the road, e.g. due to crossing overhead power lines, tram voltage supply cables or “blocking” by orientation points (“landmarks”) such as, for example, the Eiffel Tower, canopies, skyscrapers. In these cases the use of a road map to support the position determination is useful, but the aforementioned cases are still problematic. In addition, navigation systems generally operate reactively, i.e. only after the satellite-supported position sensor system has failed does one resort to alternative systems. It is disadvantageous here that there is no “anticipated blockade” prediction, nor can one have any trust in its data before the satellite-supported system fails.